Search PubMed⌕ Search

Biomedical subjects

K J Cheng

Publications and source records attributed to K J Cheng.

At least 73 records · Page 4Linked to original sources
PubMed1990

[Use of glucose and cellobiose by 3 strains of Fibrobacter succinogenes].

F succinogenes strains S85, 128 and 095 were compared with respect to their growth using glucose and/or cellobiose as the carbon and energy substrate(s) and their capacities to degrade cellulose. The growth rate of F succinogenes strain S85 was the same using glucose or cellobiose, whereas the growth rates of strains 128 and 095 were about thrice the rate when using cellobiose. Strain S85 could simultaneously use glucose and cellobiose, while strains 128 and 095 tended to use preferentially glucose then cellobiose in a mixture of the 2 sugars. Their capacities to degrade cellulose were equivalent.

Animals↗
PubMed1989

Electron microscopic, biochemical and physiological studies of Bifidobacterium pseudolongum SS-24 and Bifidobacterium thermophilum SS-19.

Comparative studies of physiology, biochemical characteristics, and morphology by electron microscopy were conducted on Bifidobacterium pseudolongum SS-24 isolated from dogs and Bifidobacterium thermophilum SS-19 isolated from swine. Both B. pseudolongum and B. thermophilum grow unusually rapidly in the rumen fluid medium of Scott and Dehority, and reached a maximum of optical density after only 6 to 7 h of incubation. B. pseudolongum and B. thermophilum showed similar patterns of results for 21 biochemical characteristics tested, with a difference found only for N-acetyl-glucosaminidase. Scanning electron micrographs revealed that B. pseudolongum produced extensive amounts of extracellular material. The cell walls of B. pseudolongum and B. thermophilum were totally different. Transmission electron micrographs of ruthenium red-stained preparations of B. pseudolongum showed a very thick (ca. 0.2 microns) Gram-positive cell wall, whereas B. thermophilum was found to have a thin (ca. 0.05 microns) Gram-positive cell wall.

Animals↗
PubMed1989

The characterization and ultrastructure of two new strains of Butyrivibrio.

Strains B-385-1 and 2-33 are numerically important components rumen bacterial populations , but they have remained (taxonomically) undefined. In spite of some resemblance to Selenomonas ruminantium in their cell size and in their formation of tufts of flagella, they more closely resemble Butyrivibrio fibrisolvens in the subpolar location of their flagella, in their guanine + cytosine content, and in most biochemical characteristics, including butyrate formation. Cells of these strains stain Gram negative, as do both Selenomonas and Butyrivibrio, but their cell walls closely resemble those of Butyrivibrio in their Gram-positive type of molecular architecture and in their cleavage pattern in freeze-etching. Cells of these strains and of B. fibrisolvens have a very thin (ca. 12 nm) peptidoglycan cell wall; thus, they fail to retain the crystal violet complex of the Gram stain and stain Gram negative. This important structural characteristic of their cell walls places strains B-385-1 and 2-33 within the genus Butyrivibrio and certain morphological and biochemical characteristics distinguish them from B. fibrisolvens.

Animals↗
PubMed1989

Composition of the rumen ciliate population in experimental herds of cattle and sheep in Lethbridge, Alberta, Western Canada.

Rumen ciliate populations were surveyed in 11 Holstein cattle and 6 sheep in Lethbridge (Alta., Canada) to determine species distribution in this Western Canadian environment. A total of 28 ciliate species were identified in cattle and 17 in sheep. The average total number of ciliates per millilitre of rumen content was 6.9 X 10(4) in cattle and 1.9 X 10(5) in sheep. The average number of species per host was 20.5 in cattle and 13.8 in sheep. Of the ciliate species detected, species of Entodinium appeared most frequently both in cattle and in sheep. Diplodinium polygonale, Eodinium lobatum, Eo. monolobum, Eremoplastron rostratum, Ostracodinium clipeolum, Os. mammosum, and Ophryoscolex purkynjei were not detected in sheep. In contrast, Ophryoscolex caudatus was not found in cattle. These data indicate that the ciliate faunas of cattle and sheep in this Western Canadian environment are similar to those found in Japan.

Alberta↗
PubMed1988

Identification of rumen bacteria that anaerobically degrade nitrite.

Fifty-one pure strains of rumen bacteria, representing 15 genera, were tested for their ability to metabolize nitrite. Twenty-five of the strains, belonging to eight genera, were capable of growth and nitrite metabolism in nitrite-containing medium sterilized by autoclaving. An additional 10 strains showed growth and nitrite metabolism in medium that was autoclaved before the addition of filter-sterilized nitrite. Nitrite metabolism was not observed in the remaining 16 strains, and these were also incapable of growth in the presence of nitrite. Ammonia was produced during nitrite reduction by Megasphaera elsdenii J1. In agreement with previous studies, abiotic losses of nitrite were observed during autoclaving and storage of media, but losses of nitrite due to bacterial metabolism were much greater.

Ammonia↗
PubMed1988

The ecology and pathogenicity of urease-producing bacteria in the urinary tract.

Urease activity is a physiological function of many bacteria that enables these organisms to utilize urea as a source of nitrogen. The association of ureolytic bacteria with human or animal hosts varies widely from a commensal relationship as demonstrated with skin microflora, a symbiotic relationship in the gastrointestinal tract, to a pathogenic relationship in the urinary tract. Since similar or identical species of bacteria such as Staphylococcus aureus are found in all three environments, the effect of urease activity on the host must be solely a function of the environment of these organisms. In this review, the importance of urease to bacteria is discussed, identifying the gastrointestinal tract as a major reservoir of ureolytic bacteria and investigating the urinary tract environment and the infectious struvite stone production that often accompanies urease-producing bacteria there. Finally, an infection model is presented which explains the development and growth of these urinary calculi and their remarkable persistence in spite of modern urological treatments.

Animals↗
PubMed1987

Interactions between Treponema bryantii and cellulolytic bacteria in the in vitro degradation of straw cellulose.

To assess the contribution of individual bacterial species to the overall process of cellulose digestion in the rumen, cellulolytic bacteria (Bacteroides succinogenes and Ruminococcus albus) were tested as pure cultures and as cocultures with noncellulolytic Treponema bryantii. In studies of in vitro barley straw digestion, Treponema cocultures surpassed pure cultures of the cellulolytic organisms in dry matter disappearance, volatile fatty acid generation, and in the production of succinic acid, lactic acid, and ethanol. Morphological examination, by electron microscopy, showed that cells of T. bryantii associate with the plant cell wall materials in straw, but that cellulose digestion occurs only when these organisms are present with cellulolytic species such as B. succinogenes. These results show that cellulolytic bacteria interact with noncellulolytic Treponema to promote the digestion of cellulosic materials.

Animals↗
PubMed1987

Electron microscopic study of the methylcellulose-mediated detachment of cellulolytic rumen bacteria from cellulose fibers.

The presence of methylcellulose prevents the attachment of cellulolytic rumen bacteria to cellulose fibers. The addition of methylcellulose to pure cultures of these organisms in which the cells are already adherent to cellulose causes their detachment from this insoluble substrate and the inhibition of their growth. Methylcellulose is not used as a carbon source by these organisms and has no effect on their growth when glucose and cellobiose are the carbon sources. Attached cells of Bacteroides succinogenes orient themselves in the plane of the individual cellulose fibers and their methylcellulose-induced detachment, which is complete (almost 100%), leaves grooves where the cellulose has been digested. Attached cells of Ruminococcus albus colonize the cellulose in a looser and less regular pattern and their almost complete methylcellulose-induced detachment leaves less regular pits in the cellulose surface. On the other hand, attached cells of Ruminococcus flavefaciens colonize the cellulose surface in a random orientation by means of a discernible exopolysaccharide network, and their less complete methylcellulose-induced detachment leaves no residual impressions on the cellulose surface. These data support the suggestion that bacterial attachment is necessary for the digestion of highly ordered crystalline cellulose, and that cellulolytic species differ in the nature of their attachment to this insoluble substrate and in the nature of their enzymatic attack. Methylcellulose is an effective agent for detaching major rumen cellulolytic bacteria from their cellulosic substrate.

Animals↗
PubMed1986

Histochemical and biochemical urease localization in the periplasm and outer membrane of two Proteus mirabilis strains.

Proteus mirabilis, a gram-negative bacillus, is often implicated in the formation of infectious kidney stones. As ureolytic activity of this organism is thought to play a major role in its pathogenesis, we adapted our recently described urease localization technique to visualize urease activity in vivo. Urease activity was ultrastructurally localized in two clinically isolated P. mirabilis strains by precipitating the enzymatic reaction product (ammonia) with sodium tetraphenylboron. Subsequent silver staining of the cells revealed urease activity to be predominantly associated with the periplasm and outer membranes of each strain. Biochemical measurements of urease activity in P. mirabilis cell fractions correlated well with histochemical observations in that the majority of urease activity was associated with the periplasm. Membrane-bound urease activity of these strains was associated mainly with the peptidoglycan in the detergent-insoluble (outer membrane) fraction.

Cell Membrane↗
PubMed1986

Enhanced degradation of 3-nitropropanol by ruminal microorganisms.

Ruminal fluid was obtained over a 4-yr period from cattle on various diets and supplements to determine the effects of different inocula on the microbial degradation of 3-nitropropanol (NPOH), a toxic metabolite in certain Astragalus spp. (Leguminosae). Nitrite (NO2-) metabolism was also studied in vitro because rapid NO2- reduction is required for the overall detoxification of NPOH. Intra-ruminal supplements of sulfite were ineffective and produced toxic signs in treated animals. Ruminal fluid from cattle on fresh pasture diets enhanced the in vitro metabolism of NO2-, but rates of NPOH disappearance were not significantly affected. Rates of NPOH degradation increased when orchardgrass pasturage was supplemented with molasses. Enhancement of NPOH degradation was achieved with supplements of nitroethane given intra-ruminally at 6.5 or 10 mg/kg body weight. The effect of nitroethane on NO2- reduction was not always observed, but the NO2- rates of metabolism always exceeded those of NPOH. The rate of NPOH degradation also increased when nitroethane was added to a molasses supplement. However, the volatility of nitroethane under field conditions prompted a search for a more stable inducer and the sodium salt of nitroethane was subsequently evaluated. The salt of nitroethane, given intra-ruminally at 20 mg nitroethane/kg body weight, resulted in the highest rate of NPOH degradation; this was similar to that reported for 3-nitropropionic acid, a nitroalkane that is much less toxic to ruminants than NPOH.

1-Propanol↗
PubMed1985

The effect of ammonia treatment on the solubilization of straw and the growth of cellulolytic rumen bacteria.

Pre-treatment of straw with anhydrous ammonia increased its susceptibility to solubilization by the predominant cellulolytic bacteria from the rumen, Bacteroides succinogenes, Ruminococcus albus and R. flavefaciens. Ammonia treatment also increased the production of microbial protein and fermentation products by all three species. Scanning electron microscope observations of straw during digestion suggested that the attack of straw by these bacteria was accompanied by the formation of substantial numbers of adherent microcolonies.

Ammonia↗
PubMed1985

Cytochemical Localization of Urease in a Rumen Staphylococcus sp. by Electron Microscopy.

We describe a technique whereby intracellular urease activity can be localized by transmission electron microscopy. The ammonia produced from the enzymatic hydrolysis of urea is first precipitated with sodium tetraphenylboron and then replaced with silver to produce electron-dense silver tetraphenylboron. This direct reaction product deposition procedure was used to demonstrate the presence of membrane-bound urease of Staphylococcus sp. H3-22, a gram-positive ruminal bacterium.

Journal Article↗
PubMed1983

Effects of breed, diet and sex on the alkaline phosphatase activity in walls of the bovine rumen and abomasum.

Alkaline phosphatase (APase) activity in tissue samples, with adherent bacteria, was measured from two sites in the rumen and from two sites in the abomasum of 57 yearling Angus and Hereford bulls and heifers fed a high or a low energy diet. In the rumen, APase activity was higher at the caudoventral blind sac than at the dorsal sac in animals of both breeds fed the high energy diet and in Angus bulls fed the low energy diet, but the reverse was observed in Hereford bulls fed the low-energy diet (P less than .01). In the abomasum, APase levels were higher for bulls than heifers (P less than .01) and higher at the fundic than at the pyloric region (P less than .01). Morphological studies also showed that rumen samples from animals fed a high energy diet exhibited a more widely distributed APase activity and an increase in the digestive recycling of epithelial cells that produced some "pitting" of the tissue. The higher APase activity of the epithelial tissue of animals fed the high energy diet may be explained by the greater rate of cell death and renewal indicated by the higher mitotic index reported by other researchers who have studied the cell cycle of the rumen epithelium in ruminants fed high and low energy diets.

Abomasum↗
PubMed1983

Rumen conditions that predispose cattle to pasture bloat.

Rumen contents from the dorsal sac were examined before alfalfa ingestion to determine factors that predispose cattle to pasture bloat. Chlorophyll concentration, buoyancy of particulate matter, and rates of gas production were significantly higher in cattle that subsequently bloated than in those that did not. Higher chlorophyll in bloat cases indicated accumulation of suspended chloroplast particles in the dorsal sac, perhaps due to increased buoyancy of the particulate matter. The higher fermentation rates (in the presence of glucose) suggested that the latent capacity for gas production was due to microbial colonization of suspended feed particles. Chlorophyll 4 h after feeding was also higher in bloated as compared to unbloated animals. In short, the microbial colonization and retention of particulate matter provided active inocula for promoting rapid legume digestion. Consequently, gas production was enhanced when feeding commenced, but the fermentation gases were trapped by the buoyant, frothy ingesta, resulting in the condition of pasture bloat.

Animals↗
PubMed1983

Colonization of particulates, mucous, and intestinal tissue.

The gastrointestinal system consists of myriad small ecological "niches" within which most bacteria grow in glycocalyx-enclosed microcolonies that form highly structured consortia in biofilms on the surfaces of both tissue and digesta. Bacteria in the lumen of the system are attached to their nutritive substrates by chemotaxis and they then adhere to insoluble nutrients (e.g. cellulose) or position themselves in microcolonies in locations having maximal concentrations of soluble nutrients (e.g. monomeric sugars). Thus, the digestion of even simple foods involves the simultaneous and specific colonization of many different "microniches" by bacteria. Specific bacteria have been shown to colonize tissues within the gastrointestinal tract and some of these taxonomically distinct populations have been shown to cooperate in the physiological activities of some of the colonized tissues. Highly abraded tissues and tissues exposed to extremes of acid concentration may be colonized by a single species of bacteria or yeast, because special adhesion mechanisms or acid resistance are required for persistence, but most nonsecretory epithelia within the tract are heavily colonized by a rich mixture of bacteria. We have developed techniques to retain the mucous blanket on the secretory epithelia of the intestine, and we find that the majority of bacteria and protozoa in these organs are associated with the mobile viscous layer and are thus functionally apposed to the epithelial tissues. Notable exception are the bacteria and protozoa that adhere avidly to the epithelial tissues by special adhesion mechanisms and must therefore remain stationary within the mobile mucous blanket.

Animals↗
PubMed1982

Electron micrographic study of precipitates formed by interaction of silicic acid and alkaline phosphatase: contribution to a study of silica urolithiasis in cattle.

Association of alkaline phosphatase with silicic acid in precipitates formed in dilute solution was studied as a model for the nonspecific reaction between silicic acid and protein. Precipitates contained 68-83% of the silicic acid and 52-83% of the enzyme in the original mixture and were in the form of aggregates of roundish particles 150-800 nm in diameter. Enzyme protein formed a tightly bound layer on the surface of particles formed in solutions of freshly prepared silicic acid. The similarity between the ultrastructural features of precipitates from solutions of silicic acid and of internal portions of siliceous urinary calculi from cattle suggests that deposition of silica during development of such calculi is due, at least in part, to the interaction of protein with silicic acid in urine.

Acid Phosphatase↗